Microorganisms, such as fungi or bacteria, are generally found on all surfaces which surround us in everyday life. Although the bacteria or fungi that are present on the surfaces are typically harmless to humans, there are high hygiene standards specifically in sensitive areas, such as in the food industry and in medicine, for example, these standards envisaging a very low microbe count. In these two areas specifically, microbe-free surfaces are required, which can be realized only through the use of microbicidal chemicals. Such surfaces are equipped, accordingly, with biocides, in order to prevent the uncontrolled propagation of microorganisms. Microorganisms require only minimal amounts of nutrients; for example, often just a few dust particles, with appropriate atmospheric humidity, may be sufficient for their growth. Therefore, numerous building materials, such as wood, plaster, stone, metals, and their coatings, for example, constitute a nutrient substrate for microorganisms. The microorganisms present not only are harmful to the persons that come into association with the surfaces of these building materials, but may also themselves contribute to the destruction of the building materials and hence of the built structures, by attacking and destroying the components and/or their protective coats.
Thus, for example, a mold infestation in interiors harbors a high allergenic and health risk. The allergenic effects of a number of species of mold are already known. In practice it is appropriate to adopt a policy of minimization, since even hitherto unobtrusive species may have a sensitizing effect. A further danger is formed by the molds which form mycotoxins.
The growth of the microorganisms is further promoted by external circumstances, such as high atmospheric humidity, especially in kitchens and bathrooms, minimal or absent ventilation of rooms, and also constructional circumstances, such as cupboards which stand close to the wall, etc. A further factor which contributes to an increased incidence of microorganisms in interiors is the improved insulation of the external walls and the windows. This leads to increased colonization of façades and internal walls by algae and fungi. The atmospheric moisture condenses on the cold walls and forms the conditions that are needed for growth.
To protect against microorganisms, the surfaces and articles are treated, in the event of damage or preventively, with biocidal chemicals. These chemicals are frequently compounds of low molecular mass, in many cases toxic to humans as well, which are applied directly or in solution. Typically these compounds, on account of their chemical structure and small size, penetrate into the cells of the microorganisms, where they alter structures and kill them off. These compounds, known as microbiocidal substances, are capable of killing off the microorganisms or, as microbiostatic substances, of inhibiting growth or propagation of the microorganisms, without killing off the microorganisms themselves. Microbicidal substances include algicides, bactericides, fungicides, etc.
In addition there is the class of the contact microbicides, which enter into contact only with the cell membrane of the microorganisms, where they influence the growth and the spread of the microorganisms. However, microbicides are typically used up in the surfaces over time, and therefore do not afford any lasting protection.
Amine-containing biocidal actives are known from the literature in the form, for example, of quaternary ammonium compounds (QUATS). They possess a broad spectrum of action with respect to fungi. The activity is based on the presence of at least one long alkyl chain on the nitrogen atom. This interacts with the cell surface of the microorganisms and thereby hinders their growth. QUATS are mostly water-soluble and are employed in aqueous solutions. It is, however, also conceivable to carry out functionalization of QUATS and to attach them covalently into a polymer, as proposed for example in EP 1 194 434 B1.
The activity of polymers with secondary amino functions has already been described. Thus it is apparent from EP 0 862 858 that copolymers of tert-butylaminoethyl methacrylate inherently possess microbicidal properties. DE 10024270 A1 describes antimicrobial polymers comprising alkylacrylamides, which, themselves or as a polymer blend, equip surfaces lastingly with antimicrobial action and, moreover, are resistant to solvents and physical stresses.
Amine-modified siloxanes are known for use as softeners in the textile industry. Among others, DE 197 39 991 A1 describes aminosiloxane-polyether polymers for textile treatment. The compounds are described for use as wetting agents and dispersants, additives in fabric softeners, or antifoam powders. The functional groups of the polymers described therein are connected via Si—C and via Si—O—C bonds. The process for preparing the aminosiloxane-polyether polymers described therein takes place through condensation reactions of various silanes—and/or siloxane starting materials and polyether glycols, with elimination of constituents of low molecular mass.
DE 3928867 describes amino-functional polysiloxane-polyoxyalkylene block copolymers for the cell opening of rigid polyurethane foams. U.S. Pat. No. 3,389,160 discloses organomodified siloxanes with dialkylamino- and hydroxy-functional groups. In contrast to the modified siloxanes described here, they do not contain hydrophilic groups, e.g., polyether-functional groups. The area of application of these molecules lies in corrosion control or as surfactants for aqueous systems. None of these documents describes an antimicrobial effect of these amine-modified polysiloxanes.
DE 68921781 describes organosilicon-containing quaternary ammonium compounds and their antimicrobial activity. The compounds in question, however, are silane compounds, and not polysiloxanes. DE 4243399, finally, describes organopolysiloxane compounds with guanidyl groups, which possess an antibacterial activity. Surface-active aspects remain unconsidered.
Furthermore, DE 199 39 866 and U.S. Pat. No. 4,541,936 disclose organopolysiloxanes in aqueous or organic compositions for the treatment of paper and/or wood and wood products. No microbicidal—fungicidal, for example—effect of the amine-modified siloxanes described therein is stated.
In relation to the prior art identified above, therefore, it is an object of the present invention to provide for the use of compounds in protecting agents, such as surface-coating systems, which protect surfaces of workpieces or the workpieces themselves, examples being lignocellulosic materials, such as wood and woodbase materials, from microbial infestation.